As part of an automatic transmission for motor vehicles, a radial piston pump has been disclosed in DE-A1 41 39 611 and serves for supply of lubricant and supply of control and actuation devices. The driving part of the radial piston pump is preferably connected with a starting device front-mounted on the transmission wherein the eccentric for driving the individual pistons can be connected, e.g. with an impeller of a hydrodynamic torque converter.
The cylinder bores of the radial piston pump are usually outwardly sealed in radial direction by a stopper which has a central through hole, all stoppers of the radial piston pump are covered by a common flat spring which acts as return valve. In order to obtain a better actuation of the flat spring by the delivery pressure, the stoppers are provided on their upper side with grooves that extend in parallel and end within the processed sealing surface of the frontal surfaces and are aligned in peripheral direction of the radial piston pump. The flat spring seals both the centrally disposed bores and the grooves against a collecting annular groove lying radially outside the stoppers. During delivery of the radial piston pump, the flat spring on those stoppers which lie in the pressure zone of the radial piston pump is lifted from the sealing surface by the pressure in the central bore and in the grooves.
In the area of the radially outwardly oriented edge of the pistons, there is situated in the pump housing, coaxially with the pump axle, a suction annular groove which cuts the cylinder bores. The cutting forms suction openings between the suction annular groove and the cylinder bores. A suction throttle is formed on each piston between the edge and the respective suction opening.
However for certain applications, it is required to enlarge the outflow cross section from the cylinder chamber.
The problem on which this invention is based is to provide a radial piston pump which, compared with the conventional radial piston pumps, has an increased outflow cross section adapted to the intended application.
According to the invention, each stopper pressed into the housing is equipped with at least one side discharge channel the diameter of which, together with that of the central bore, determines the outflow cross section; when the diameter of the central bore remains the same, the outflow cross section can be adapted to the conditions of use by adequate dimensions of the side discharge channels.
The advantage is to initially provide side discharge channels when the stopper is initially formed from a raw material, since this considerably reduces the cost of production. At the same time, the position fixing of the stoppers is made easier when pressed into the housing. The additional discharge channels offer the further advantage that the sealing flat valve has only a very small differential pressure surface and thus opens easily. The flat valve is passed as formerly in the stopper.
In the inventive radial piston pump, peripheral grooves are also provided in the housing whereby the cost of production is considerably reduced thereby preventing an adherence, i.e. a sticking of the flat valve to the housing. Instead of the peripheral grooves, individual sectors are also provided with grooves which are associated with the individual piston bores and the connection to which the stoppers make possible.
Since the stoppers are pressed into the housing in a desired direction, it is possible to economically produced twisted discharge grooves. In every case, the stoppers seal over the entire outer diameter of the cylinder bores containing the pistons, whereby the flat valve seat is not disconnected.